Grain mill



FIG. 1 is a perspective view of one side and end of a grain mill showing my new design;

FIG. 2 is a perspective view of the other side and end of the grain mill shown in FIG. 1;

FIG. 3 is a top view of FIG. 1; and

FIG. 4 is a bottom view taken of FIG. 1. 

The ornamental design for a grain mill, as shown and described. 